The production of rigid polyurethane (PU) and polyisocyanurate foams from organic polyisocyanates and polyester or polyether polyols having an average of two or more hydroxyl groups per molecule has been well established over the past several decades. These foams have played an increasingly important role in the construction, refrigeration and packaging industry due to their excellent insulation properties. Multimillion pounds of rigid PU and polyisocyanurate foams are used annually for this purpose.
The vast majority of these foams utilize chlorinated fluorinated hydrocarbons (CFCs) as the blowing agents. These have come under intense environmental concern due to their ozone-depleting properties. More recently, the second generation hydrogenated chlorinated fluorinated hydrocarbon (HCFCs) emerged as replacements for CFCs; these are believed to be substantially less ozone-depleting than the CFC's A number of other blowing agents such as low boiling hydrocarbons such as pentane have also been cited but with no commercial success. Replacement of CFCs and HCFCs with water (CO.sub.2 blown) using commonly available polyols produces foams with inferior initial and aged thermal conductivities (K-factors). Other physical properties, deficiencies are increased mold release time, poor flow, decreased dimensional stability and increased open cell content which in turn contribute to poor insulation properties. Through the use of modified polyols, in particular the amine-based polyols, surfactants, and blowing agents such as, chlorofluorocarbons or hydrofluorochlorocarbons with or without water, rigid foams have been prepared in experimental quantities which have low K-factors. Attempts to use water (CO.sub.2) as the sole blowing agent (100% H.sub.2 O blown) result in foams which have severe K-factor and physical properties deficiencies. At molded core densities of greater than 2 PCF (pounds per cubic foot), K-factors for all CO.sub.2 blown foams are 25-30% higher than for example with CFC-11. These increase substantially during aging under ambient conditions. At densities of lower than 2 PCF (32.03 Kg./cu. meter), K-factors increase drastically, since the foams tend to shrink during heat and cold cycles resulting in increased surface friabilities.